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Modelling of supercritical turbulent flow over an inclined backward-facing step in a open channel
Příhoda, Jaromír ; Zubík, P. ; Šulc, J. ; Sedlář, M.
The contribution deals with the experimental and numerical modelling of supercritical turbulent flow in an open channel with an inclined backward-facing step on its bottom. The step with the height 100 mm and the inclination angle 20 deg was placed in the water channel of the cross-section 200x200 mm. Experiments were carried out by means of the PIV and LDA measuring techniques. Numerical simulations were executed by the commercial software ANSYS CFX 12.0. Numerical results obtained by the two-equation SST model and the EARSM model completed by transport equations for turbulent energy and specific dissipation rate were compared with experimental data. The modelling was concentrated particularly on the flow pattern near the step including the possible flow separation and the corresponding changes of free surface. The agreement of numerical results obtained by means of the EARSM model with experimental data is quite good.
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GPU computation in engineering practice
Fischer, Cyril
In many research fields the numerical problems demand extremely large computational power. As a consequence, researchers are constantly demanding new and more powerful computers. Recently, the graphics chip producer NVIDIA launched the CUDA parallel computing architecture, which enables scientists to utilize the extreme power available on modern and relatively cheap Graphical Processor Units (GPUs). Necessity to change the common approach together with significant difference in the GPU architecture prevents the wide usage of the graphics hardware.
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Numerical Simulations of Recovery Heat Exchangers
Novotný, P. ; Vít, T. ; Dančová, Petra
This paper is focused on evaluation and comparison of air-air heat exchangers of plate type used for retrieving the heat from the waste air. The first part of this paper shows how it is possible to evaluate and compare each exchanger with another one. Process and procedure of numerical simulation is described in the main part. The procedure involves selecting an appropriate geometry of the exchanger, computational mesh generating, defining boundary conditions and the choice of a viscous flow model. Three geometrical types of heat transfer surface were compared in this work. Results of numerical simulations were compared with experimental measurement.
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Experimental investigation of synthetic jet array
Dančová, Petra ; Vít, Tomáš ; Kotek, M.
Paper deals on an experimental investigation of a synthetic jet array. This investigation focuses on a partial problem of the general task “a synthetic jet array interacting with a channel flow”. The experiments have been performed with water as a working fluid using hot-wire anemometry, laser Doppler vibrometry and particle image velocimetry methods.
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HYBRID-SYNTHETIC IMPINGING JETS
Tesař, Václav
Impinging jets can achieve the highest convective heat or mass transfer rate. An increase beyond present limits is possible by pulsation of the flow. The extreme case of the synthetic jets could be particularly effective – were there not the re-ingestion of the fluid. A solution brings the new concept of non-zero time mean hybrid synthetic jet.
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Excitation of rotating disk by stationary permanent magnets
Půst, Ladislav ; Pešek, Luděk
Abstract: Flexural vibrations of rotating disk contain forward and backward traveling waves can be excited at certain speed of rotating disk also by a standing constant single point force or by multiple points standing forces, realized e.g. by permanent magnets fixed in non-rotating space. Presented paper is contribution to the theoretical background of a new experimental excitation technique elaborated in Institute of Thermomechanics for investigation of a bladed turbine disk model with imperfection by addition several damping heads on ends of blades. Mathematical model of imperfect rotating disk was derived by using data gained experimentally and by FE computed for three lowest split modes of vibrations. It was shown how either the whole spectrum of modes of vibrations can be recorded or some resonance of selected mode can be suppressed on emphasized by means of appropriate number and positions of permanent magnets.
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Microstructural models of trabecular bone - comparison of CT-based FE models
Jiroušek, Ondřej ; Zlámal, Petr
In the article a detailed comparison of techniques used to developed detailed FE models of trabeculra bone microstructure is presented. The FE models are built using a stack of microtomographic images of trabecular bone. Compression test of a cylindrical sample taken from human proximal femur is virtually performed using FE models developed using different procedures. Effect of improper segmentation, mesh smoothing, mesh density, use of hexahedral/ tetrahedral elements, linear/ quadratic shape function is evaluated in parametric study. Material model is based on nanoindentation and numerical elastic properties of sample are compared to experimental results.
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